Pulsus paradoxus
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In [[medicine]], a '''pulsus paradoxus''' (PP), also '''paradoxic pulse''' and '''paradoxical pulse''', is an exaggeration of the normal variation in the pulse during the inspiratory phase of respiration, in which the pulse becomes weaker as one inhales and stronger as one exhales. It is a [[Medical sign|sign]] that is indicative of several conditions including [[cardiac tamponade]], [[pericarditis]], chronic [[sleep apnea]], [[croup]], and [[obstructive lung disease]] (e.g. [[asthma]], [[chronic obstructive pulmonary disease|COPD]]).<ref name=khasnis_12082330>Khasnis A, Lokhandwala Y. Clinical signs in medicine: pulsus paradoxus. J Postgrad Med. 2002 Jan-Mar;48(1):46-9. PMID 12082330. [http://www.jpgmonline.com/article.asp?issn=0022-3859;year=2002;volume=48;issue=1;spage=46;epage=9;aulast=Khasnis Free Full Text].</ref>
The ''paradox'' in ''pulsus paradoxus'' is that, on [[clinical examination]], one can detect extra beats on [[cardiac auscultation]], during inspiration, when compared to the [[radial artery|radial]] [[pulse]].<ref name=khasnis_12082330/> It results from an accentuated decrease of the blood pressure, which leads to the (radial) pulse not being palpable and may be accompanied by an increase in the [[jugular venous pressure]] height ([[Kussmaul sign]]). As is usual with inspiration, the [[heart rate]] is increased,<ref>{{cite journal |author=Guntheroth W, Morgan B, Mullins G |title=Effect of respiration on venous return and stroke volume in cardiac tamponade. Mechanism of pulsus parodoxus |journal=Circ. Res. |volume=20 |issue=4 |pages=381–90 |year=1967 |pmid=6025402}} [http://circres.ahajournals.org/cgi/content/abstract/circresaha;20/4/381 Abstract]</ref> due to decreased <!-- it is systemic venous return --> left ventricular output.<ref>{{cite journal |author=Soucek M, Kára T, Jurák P, Halámek J, Spinarová L, Meluzín J, Toman J, Rihácek I, Sumbera J, Frána P |title=Heart rate and increased intravascular volume |journal=Physiological research / Academia Scientiarum Bohemoslovaca |volume=52 |issue=1 |pages=137–40 |year=2003 |pmid=12625819}} [http://www.biomed.cas.cz/physiolres/pdf/52/52_137.pdf Free Full Text].</ref>
==Mechanism of reduced blood pressure during inspiration in normal conditions==
During inspiration, systolic blood pressure decreases, and pulse rate goes up. This is because the intrathoracic pressure becomes more negative relative to atmospheric pressure. This increases systemic venous return, so more blood flows into the right side of the heart. However, the decrease in intrathoracic pressure also expands the compliant pulmonary vasculature. This increase in pulmonary blood capacity pools the blood in the lungs, and decreases pulmonary venous return, so flow is reduced to the left side of the heart. Reduced left-heart filling leads to a reduced stroke volume which manifests as a decrease in systolic blood pressure. The decrease in systolic blood pressure leads to a faster heart rate due to the baroreceptor reflex, which stimulates sympathetic outflow to the heart.
==Measurement of PP==
PP is quantified using a [[blood pressure cuff]] and stethoscope, by measuring the variation of the pressure in [[systole]] with [[Respiration (physiology)|respiration]]. Normal systolic [[blood pressure]] variation (with respiration) is considered to be ≤10 [[mmHg]].<ref name=khasnis_12082330/> Pulsus paradoxus is an inspiratory reduction in systolic pressure >10 mmHg. Pulsus paradoxus can also be measured by listening to [[Korotkoff]] sounds and hearing the actual sound of the systolic beat. If the pressure gradient is >10mmHg, it can be classified as pulsus paradoxus and shifting of the atrial septum.
==Predictive value for tamponade==
PP has been shown to be predictive of the severity of cardiac tamponade.<ref>Curtiss EI, Reddy PS, Uretsky BF, Cecchetti AA. Pulsus paradoxus: definition and relation to the severity of cardiac tamponade. Am Heart J. 1988 Feb;115(2):391-8. PMID 3341174.</ref>
==Causes==
Pulsus paradoxus can be caused by several physiologic mechanisms. Anatomically, these can be grouped into:<ref name=khasnis_12082330/>
*''cardiac causes'',
*''pulmonary causes'' and
*''non-pulmonary and non-cardiac causes''.
Considered physiologically, PP is caused by:
*decreased right heart functional reserve, e.g. myocardial infarction and tamponade,
*right ventricular inflow or outflow obstruction, e.g. superior vena cava obstruction and pulmonary embolism, and
*decreased blood to the left heart due to pulmonary vasodilation/hyperinflation, e.g. asthma, COPD and anaphylactic shock.
===List of causes===
Cardiac:
*[[cardiac tamponade]]
*[[pericardial effusion]]
*[[pulmonary embolism]]
*[[cardiogenic shock]]
Pulmonary:
*[[tension pneumothorax]]
*[[asthma]]
Non-pulmonary and non-cardiac:
*[[anaphylactic shock]]
*[[superior vena cava]] obstruction
==References==
<references/>
==See also==
*[[Precordial exam]]
*[[Pulsus alternans]]
==External links==
*[http://www.jpgmonline.com/article.asp?issn=0022-3859;year=2002;volume=48;issue=1;spage=46;epage=9;aulast=Khasnis Clinical signs in medicine: pulsus paradoxus] - Mechanism, pathophysiology, detection and management of patient with pulsus paradoxus.
[[Category:Medical signs]]
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